Drafting instrument



April 18, 1939. w. J. KALLlO DRAFTING INSTRUMENT Filed March 2, 1957 i g A II I INVENTOR. Mu/4W d flux/0.

ha/10L C ATTORNEY.

Patented Apr. 18, 1939 UNITED STATES PATENT OFFICE 1 Claim.

My invention relates to drafting instruments and my improvements contemplate an improved construction and one by which lines and points can be located and angles measured with facility and accuracy throughout a large range of angles.

I secure this object in the construction shown in the accompanying drawing, in which:---

Figure l is a plan view of an instrument embodying my invention, approximating a 45 degree triangle in shape.

Figure 2 is a section on the line B-B, Figure 1.

Figure 3 is a section on the broken line C-C, Figure 1.

Figure 4 is a detail plan View to an enlarged scale of a portion of said instrument illustrating in part a modified construction, a portion being broken away.

Figure 5 is a section on the line E-E, Figure 4.

The body of the instrument is made up of two parts 2 and 3 which I prefer to have of transparent celluloid.

The part 2 has the edges 20-2?) and 2b 2o at right angles to each other. The side 217-20 is longer than the side 2a2b. From the point 2a an edge extends inward at an angle of 45 with the edge Za-Zb to a point 211, it then extends in an inwardly curving arcuate form to the point 2e, somewhat further into the part 2 than the point 2d.

From the point 2e, the edge extends to the point 2f at an angle of approximately 45 to the edge 2a2b, from which point it extends in a straight line to the point 20.

The part 3 has two approximately parallel edges 3a3b and 30-311 and is formed at one end to fit the arcuate edge 2d-2e and turn about its center, and at the other end to fit against the straight edge 2f-2c. The edges 3c-3d and 2e2f do not come quite into contact but have a little distance left between them. The edges 3a3b and 2b2c are at an angle of 45 to each other.

4 is a hinge-plate secured to the parts 2 and 3, at adjacent surfaces of said parts and holding said parts in the same plane. 5 is a hollow rivet passing through the plate 4 and part 3 at the center of the arcuate edge 2d2e. 5a is a bronze washer around the shank of the rivet 5, forming a bearing part that turns with the part 3 about said rivet and coaxial therewith. 6 are rivets by which the plate 4 is secured to the part 2. I have used a steel plate and rivets for the parts 4 and 6, but contemplate using celluloid for the plate and other means of fastening.

1 is an index plate secured at one end to the part 3, extending over the surface of the part 2, and having an arcuate edge 1a the center of which is at the center of the rivet 5 and axis about which the plate 3 turns. The edge 1a 5 is divided into a scale of degrees which is to be read by reference to the datum point 29 upon the plate 2 and is preferably directly and reversely numbered as shown in Figure 1.

8 is a line upon the surface of the part 3, radiating from the axis about which said plate turns at the center of the rivet 5, and extending parallel to, and well within the edges of said part in a direction which if extended would pass through the 45-degree mark of the scale, on15 the edge 212-20. 8a is a hole through the part 3 having its center in the line 8 and at a distance from the center of the rivet 5.

The edge 2b2c is marked to indicate degrees of angles centering at the axis of the rivet 5 and a base line extending from said axis parallel to the edge 2a--2b.

The plate I may be of Celluloid or other transparent material and is cut out at its center forming an opening which preferably has an arcuate edge 10 with its center at the axis of the rivet 5.

9 is a scale of degrees marked upon the surface of the part 2, which may be seen through the plate I, the opening in said plate, and beyond the edge thereof, to read an angle about the axis of the rivet 5 a bounding line of which angles does not extend to the edge 2b--2c.

lb is an arcuate slot through the plate I having its center at the center of the rivet 5. Illa is a screw-threaded bolt fastened to the plate 2 at its lower end and extending through the slot lb. I0 is a thumb nut upon the bolt Illa, adapted to be screwed down upon the plate I to fix the relative positions of parts 3 and 2. With the parts in the position shown in full lines in Figure 1, the edges are firmly in contact and the angle between the edges 3a-3b and 2b-2c is 45.

The method of using the above described device is as follows:

The instrument may be centered by sight or by passing a sharp pencil through the hollow of the rivet 5, as indicated in broken lines in Figure 2, the point of the pencil engaging the assigned center. The instrument may then be turned about this center until the zero line upon the edge of the scale 2b2c corresponds to the required position with reference to which an assigned angle is to be drawn. The required angle,

if less than may be marked at the edge 2b2c by reference to the scale on said edge.

If a greater angle than 45 is required, the thumb nut I0 is loosened and the part 3 turned as indicated in broken lines in Figure 1, until the additional angle required is indicated on the scale ?a by the relative position of the datum point 29, and a pencil point is passed through the hole 8a to mark a point on the paper through which the required radial line may be drawn.

In reading an angle the instrument is centered and located as above described and the angle noted by means of the scale along the edge 217-20, or if a bounding line of the angle is too short for this, then by the scale 9. If the angle is greater than 45, the part 3 is turned about its axis until the line 8 registers with the bounding line of the angle, as above described, and the additional angle noted or may be read directly by the reverse numbering of the scale 10.

If desired, a transparent disc II with cross lines I la on its surface (Figs. 4 and 5) may be placed in the lower end of the tubular bore of the rivet'5, and this may be used to accurately locate the axis of the part 3 above a required center.

The engagement of the part 3 at the lines 2f--- 20 and 3a-3c, and the arcuate edge 2d2e together with the plates 4 and 1 make a firm connection and the edges 2b'2c and 3a3b afford the facilities of a 45 triangle.

The contact of the parts 2 and 3 at the lines 2f2c and at the arcuate edge 2d2e are somewhat opposed to each other so that an and firm engagement is secured.

What I claim is:-

A triangle having a longer and a shorter straight edge meeting at an angle and forming two sides of the triangle and a third edge extending from the end of said shorter edge remote from its junction with said longer edge in a direction parallel to the third side of the triangle to a point spaced a relatively short distance from said longer edge and then extending to the end of said longer edge remote from its junction with said shorter edge, and a second part pivoted to the first named part adjacent to said end of said shorter edge, said second part having an inner edge adjacent and registering with the third edge of the first named part and an outer edge forming the third side of the triangle and meeting said longer edge of the first named part at said end thereof, said longer edge being provided with an angle scale with said pivot as its center said scale extending toward said end of said longer edge to a point beyond that at which the first portion of the third edge of the first named part would have out said longer edge if extended, said second part being transparent and having a line thereon extending radially from said pivot parallel to the outer edge of said second part so that it would register with a division of said scale if extended, and means for indicating the angular distance said second part shall have turned about said pivot, said second part having a perforation therethrough in said line.

accurate WILLIAM J. KALLIO. 

